Fuel system

ABSTRACT

A fuel system  10  which selectively receives, stores and delivers volatile fuel  16 . Fuel system  10  includes a variable volume fuel tank  12  having a movable piston  22  which is attached to a pair of bellows diaphragm members  26, 28 . Members  26, 28  selectively contract and expand to move piston  22  within tank  12 , effective to alter the volume of the fuel containing portion  14  of tank  12 , thereby maintaining fuel  16  in a pressurized state and substantially preventing the accumulation of vapors within tank  12.

FIELD OF THE INVENTION

The present invention generally relates to a fuel system and moreparticularly, to a vehicular fuel system which includes a variablevolume fuel tank and which receives, stores, and selectively deliverspressurized fuel to an internal combustion engine without using aconventional fuel pump.

BACKGROUND OF THE INVENTION

Vehicular fuel systems are adapted to selectively receive and store fuelfor use within and/or by an engine (i.e., an internal combustion typeengine), effective to allow a vehicle to be desirably driven andmaneuvered.

Conventionally, these assemblies include a tank containing volatile orvaporific fuel, and an electric pump for delivering fuel from the tankto an internal combustion engine. Certain drawbacks, however, areassociated with the use of these conventional fuel pumps. For exampleand without limitation, conventional fuel pumps often cause and/or allowundesirable fuel vapor bubbles to be formed within the fuel which reduceengine performance and efficiency.

Additionally, these prior types of fuel systems allow fuel which isstored within the tank to vaporize or evaporate. This fuel vaporcollects above the fuel in the tank and may undesirably escape into theatmosphere. As a result of governmental regulation of emissions of thisfuel vapor, automobile manufacturers have devised numerous methods anddevices to selectively purge vapors from the tank, and to treat andcontrollably release such vapors into the ambient environment. Thesemethods and devices undesirably add to the expense of the vehicle andmay also allow some of the fuel vapors to undesirably escape into theatmosphere.

Attempts have been made to utilize a variable volume fuel tank forcompressibly pressurizing the fuel within the tank in order to preventfuel vaporization during the fuel delivery process. This type ofvariable volume fuel tank includes a piston which is movably disposedwithin the tank and which separates the tank into two volumes (e.g., onevolume filled with fuel and one volume filled with pressurized air). Theair is typically provided by a regulator which can be controlled by amicroprocessor. The position of the piston is controlled in order tomaintain the fuel at a relatively high pressure, thereby substantiallyreducing fuel vaporization. While this type of fuel delivery systemsolves many of the problems associated with conventional fuel systems,it does suffer from several drawbacks.

For example and without limitation, in order to prevent air frompermeating the fuel, several relatively tight seals must be operativelydisposed on the piston. These seals typically contact the housing of thetank and a guide rod on which the piston is disposed. These sealsundesirably generate a relatively high amount of drag and may stillallow an undesirable amount of air or vapor to permeate the fuel.Furthermore, these prior fuel systems utilize a spring and a pressurecontrolled clutch mechanism to allow the piston to retract duringrefueling. These clutch mechanisms undesirably increase the cost andcomplexity of the system. Moreover, these systems do not always providesufficient delivery of fuel to the engine during system recharging anddo not include a method or apparatus for extracting air that may bedissolved within and subsequently released from the fuel.

The present invention provides an improved pumpless fuel system whichincludes a variable volume fuel tank and which addresses the previouslydelineated drawbacks of prior fuel systems while concomitantly allowingfuel to be temporarily stored and communicated to an engine in anefficient and desired manner.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a fuel systemwhich overcomes at least some of the previously delineated drawbacks ofprior fuel systems.

It is a second object of the present invention to provide a fuel systemwhich includes a variable volume fuel tank for compressibly pressurizingthe fuel within the fuel tank, thereby reducing the likelihood ofundesirable fuel vapor emission.

It is a third object of the present invention to provide a fuel systemwhich includes a variable volume fuel tank having a movable piston withreduced drag characteristics.

It is a fourth object of the present invention to provide a pumplessfuel system which includes an apparatus for extracting air that may bedissolved within and subsequently released from the fuel.

According to a first aspect of the present invention, a fuel system isprovided. The fuel system includes a variable volume fuel tank includinga first portion which selectively receives and contains an amount offuel, and a second portion which selectively receives and contains anamount of pressurized gas; a piston which is movably disposed within thevariable volume fuel tank; and at least one bellows member which isdisposed within the tank, which at least partially defines the secondportion of the tank, and which is coupled to a back surface of the tank,the at least one bellows member being selectively movable from a firstcontracted position to a second expanded position, the movement of thebellows member being effective to cause the piston to move within thevariable volume fuel tank and to compressibly pressurize the amount offuel.

According to a second aspect of the present invention, a method isprovided for pressurizing an amount of fuel contained within a firstportion of a fuel tank. The method includes the steps of providing apiston; movably disposing the piston within the fuel tank; providing atleast one selectively expandable diaphragm; sealably connecting a firstend of the at least one selectively expandable diaphragm to a backsurface of the fuel tank, the at least one selectively expandablediaphragm being effective to define a second portion of the fuel tankwhich is sealably separated from the first portion of the fuel tank; andselectively introducing pressurized gas into the second portion of thefuel tank, effective to cause the at least one selectively expandablediaphragm to expand, thereby causing the piston to move within thevariable volume fuel tank and to compressibly pressurize the amount offuel.

These and other aspects, features, and embodiments of the presentinvention will become apparent from a reading of the following detaileddescription of the preferred embodiment of the invention and byreference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a fuel system which ismade in accordance with the teachings of the preferred embodiment of theinvention.

FIG. 2 is a graph representing the pressure exerted upon the piston ofthe fuel system shown in FIG. 1 as a result of the fuel residing withinthe system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

Referring now to FIG. 1, there is shown a fuel system 10 which is madein accordance with the teachings of the preferred embodiment of theinvention, and which is adapted for use within an automotive vehicle. Asshown, fuel system 10 includes a generally cylindrical container,housing, or tank 12 having a fuel-containing portion 14 which has avariable volume and which selectively receives and stores an amount ofliquid fuel 16, and a second portion 18 which is sealed from the firstportion and which selectively receives and contains an amount ofpressurized air or gas 20. A piston 22 is movably disposed within tank12 and more particularly, is slidably disposed upon a guide rod ormember 24 which is conventionally and longitudinally mounted within tank12. A pair of selectively expandable and collapsible “bellows” membersor diaphragms 26, 28 are coupled to movable piston 22 and to tank 12.Particularly, outer bellows member 26 is sealably connected to the outerlip 30 of piston 22 by use of a conventional seal, clamp or ring 32, andis sealably connected to the periphery of the back surface 34 of tank 12by use of a conventional seal, clamp or ring 36. Inner bellows member 28is sealably connected to the inner lip 38 of piston 22 by use of aconventional seal, clamp or ring 40, and is sealably connected to theback surface 34 of tank 12 and/or around a rear portion of rod 24 (e.g.,the portion of rod 24 contacting the back surface 34 of tank 12) by useof a conventional seal, clamp or ring 42. Bellows diaphragms 26, 28 andseals 32, 36, 40 and 42 cooperate to retain pressurized air or gas 20within portion 18 and to prevent any air or gas 20 from escaping intofuel 16 (e.g., bellows members 26, 28 cooperatively define portion 18).Each bellows member 26, 28 includes several “bellows” or selectivelyexpandable pleats 44 which are adapted to selectively expand orcontract, thereby expanding and contracting the respective diaphragms26, 28. In the preferred embodiment of the invention, diaphragms 26, 28are made from a durable corrosion-resistant material such as a polymeror nylon material. In other non-limiting embodiments, diaphragms 26, 28may be other types of selectively expandable diaphragms, and in onenon-limiting embodiment, guide rod 24 is eliminated and a singlediaphragm is used to move piston 22. In this alternate embodiment, thesingle diaphragm may have one “open” end which is sealably connected tothe back surface 34 of tank 12 and one “closed” end which contacts thepiston.

A conventional fuel filler pipe or conduit 46 is communicativelyconnected to portion 14 and allows fuel to be selectively delivered tofuel tank 12. Fuel filler pipe 46 includes a conventional nozzlereceiving apparatus (not shown), which in one non-limiting embodiment issubstantially identical in structure and function to the nozzlereceiving end and apparatus described in U.S. Pat. No. 5,526,795 ofThompson et al. (the “'795 patent”) which is assigned to the presentassignee and which is fully and completely incorporated herein byreference. Fuel filler line 46 includes an anti-expulsion valve ordevice 54 (e.g., a one-way check valve) which prevents fuel from beingforced through line 46 when tank 12 is pressurized.

A fuel supply line, tube or conduit 48 is also fluidly andcommunicatively coupled to portion 14 and selectively carriespressurized fuel to the engine (not shown). A one-way check valve 50allows fuel or gas to flow from portion 14 to fuel supply line 48, whilepreventing fuel from flowing from line 48 back into portion 14. Aconventional pressure accumulating mechanism 52, such as the onedescribed within the '795 patent, is fluidly and communicatively coupledto fuel supply line 48 and is effective to maintain constant fuelpressure within line 48.

A pressure supply line or conduit 56 allows air or gas 20 to becontrollably communicated to portion 18. Particularly, line 56 iscoupled to a controllable source of pressurized air or gas 58 that mayinclude a conventional compressor and regulator that are controlled by aconventional microprocessor-based control unit (e.g., an engine controlunit). A one-way check valve 60 selectively and communicatively connectsportion 18 to a pressure relief line 62 and allows air and gas 20 to bepurged from portion 18.

In the preferred embodiment of the invention, tank 12 further includes avapor extraction or separation chamber or portion 64, which may beintegrally formed with and/or fluidly connected to portion 14. Chamber64 includes a tapered aperture 66 that is formed within the top surfaceof chamber 64 and which allows gas or vapor within portion 14 to beselectively transferred through tube or conduit 70. Tube 70 is coupledto a vapor storage and/or collection chamber 72 which stores and/orcollects the evaporated gas or vapor. A discharge tube 74 andcontrollably actuatable valve 76 (e.g., an electronically controlledvalve) are coupled to chamber 72 and allow the collected vapor to beselectively delivered to a treatment container or discharged forcombustion within the vehicle's engine.

Chamber 64 further includes a float member 68 which selectively engagesaperture 66 when the level of fuel 16 is substantially “full”, effectiveto close and/or seal aperture 66, thereby preventing liquid fuel fromentering into conduit 70.

In operation, pressurized air or gas is selectively introduced intoportion 18 through air input line or conduit 56, thereby causing pleats44 to expand and forcing diaphragms 26, 28 to move from a compressed orconstricted position to an expanded or extended position. As diaphragms26, 28 expand from their compressed to their expanded positions, piston22 moves in the direction of arrow 78, thereby pressurizing the fuel 16within portion 14. Additionally, any air or vapor resident withinportion 14 is forced through aperture 66 and into chamber or canister 72for storage and/or combustion within the vehicle's engine. It should beappreciated that by maintaining fuel 16 in a pressurized state, system10 substantially prevents or reduces the undesirable accumulation and/orproduction of fuel vapors within tank 12.

The use of bellows diaphragms 26, 28 provide significant “drag-reducing”benefits over prior variable volume fuel systems. Particularly, the useof bellows diaphragms 26, 28, allow piston 22 to move within fuel tank12 without the requirement of tight “drag-producing” seals between theouter lip 30 of piston 22 and fuel tank 12 and/or between the inner lip38 of piston 22 and the guide rod 24. The elimination of these sealsallows piston 22 to relatively easily move within tank 12 (e.g., in thedirection of arrows 78, 80) without a significant amount of drag,thereby desirably reducing the amount of air pressure required to movepiston 22, while continuing to prevent air or gas from leaking intoportion 14.

In the preferred embodiment of the invention, system 10 performs acontrolled depressurization of portion 18 during refueling which allowspiston 22 to move no further in the direction of arrow 80 than isrequired to depressurize the fuel and allow additional fuel to be addedto tank 12. Particularly, regulator 58 and depressurization valve 60cooperatively ensure (e.g., by the use of conventional electroniccontrol) that the pressure within portion 18 of tank 12 is equal to theaverage pressure within portion 14 of tank 12.

The pressure within portion 14 varies with the depth in the fuel tank12. Referring now to FIG. 2, there is shown a graph 90 which illustratesthe pressure within tank 12. Particularly, the vertical axis in FIG. 2represents the height in fuel tank 12 above fuel line 48, while thehorizontal axis represents pressure due to fuel within the tank. Atheight “D”, the diameter of fuel tank 12, no column of fuel exists toexert pressure on piston 22. At fuel line 48, the pressure, “P”, isapproximately equal to the “height” of the column of fuel 20 above fuelline 48, “D”, multiplied by the specific gravity of the fuel 20, “α”(i.e., P=αD). The average pressure exerted on piston 22 is representedby line 92, and in one non-limiting embodiment is equal to the distancethat rod 24 is above fuel line 48.

System 10 utilizes this average pressure to controllably depressurizeportion 14. Particularly, regulator 58 and valve 60 cooperatively ensurein a conventional manner that the pressure within portion 18 issubstantially equal to this average pressure value. In this manner, theforces exerted on piston 22 will be substantially equal on both sides ofpiston 22 and the piston 22 will move freely during refueling (e.g., inthe direction of arrow 80) and no further than the distance required todepressurize the fuel. Hence, the present system 10 allows forcontrolled depressurization and piston movement within tank 12 withoutrequiring a complex and expensive clutch mechanism.

System 10 further provides additional improvements over prior variablevolume tank systems. For example and without limitation, the airextraction portion or system of fuel system 10 (e.g., air separationchamber 64, air collection chamber 72 and purge valve 76) selectivelyallows vapor and air, which may be released from fuel 20, to beextracted from portion 14 and “purged” or combusted within the vehicle'sengine.

In alternate embodiments where fuel tank 12 is relatively large, fuelsystem 10 further includes an auxiliary electrical fuel delivery moduleor pump assembly, which may comprise a conventional type electric fuelpump. In such alternate embodiments, the fuel delivery module or pumpassembly is conventionally and operatively disposed within the tank 12and is physically and operatively coupled to the fuel supply line 48,effective to selectively cause the contained fuel 20 to forcibly enterthe line or conduit 48 and travel to the vehicle engine (not shown). Theauxiliary electric pump may be selectively activated during therecharging or repressurization of the gas or air supply 58 and/or duringtransient fuel demand conditions. In one non-limiting embodiment, theauxiliary fuel pump may replace pressure accumulator 52. In anothernon-limiting embodiment, system 10 uses the auxiliary fuel pump and theair extraction system to operate in an alternate mode in which the fuelchamber or portion 14 is predominantly under a vacuum pressure and theair chamber or portion 18 is at atmospheric pressure.

It should be understood that the invention is not limited to the exactembodiment or construction which has been illustrated and discussedabove, but that various changes and modifications may be made withoutdeparting from the spirit and the scope of the invention as is set forthin the following claims.

What is claimed is:
 1. A fuel system comprising: a variable volume fueltank including a first portion which selectively receives and containsan amount of fuel, and a second portion which selectively receives andcontains an amount of pressurized gas; a piston which is movablydisposed within said variable volume fuel tank; a guide member which islongitudinally disposed within said fuel tank and upon which said pistonis slidably mounted; and a pair of bellows members which are disposedwithin said tank, which defines said second portion of said tank andwhich are coupled to a back surface of said tank, said pair of bellowsmembers comprising a first inner bellows member and a second outerbellows member which are selectively movable from a first contractedposition to a second expanded position, said movement of said pair ofbellows members being effective to cause said piston to move within saidvariable volume fuel tank and to compressibly pressurize said amount offuel.
 2. The fuel system of claim 1 wherein said second portion iscommunicatively connected to a controllable supply of pressurized gaswhich is selectively communicated to said second portion, effective tocause said at least one bellows member to move from said firstcontracted position to said second expanded position.
 3. The fuel systemof claim 2 wherein said amount of fuel within said first portion has acertain average pressure and wherein said controllable supply ofpressurized gas is effective to cause said amount of gas within saidsecond portion to remain at approximately said certain average pressureduring refueling.
 4. The fuel system of claim 1 wherein said pistonincludes an outer lip member and an inner lip member and wherein saidfirst inner bellows member is sealably connected to said inner lipmember and said outer bellows member is sealably connected to said outerlip member.
 5. The fuel system of claim 4 wherein said fuel tank isdisposed within an automotive vehicle.
 6. The fuel system of claim 1further comprising a separation chamber which is fluidly connected tosaid first portion, said separation chamber including an aperture whichselectively allows an amount of vapor to be discharged from saidseparation chamber and a float member which selectively seals saidaperture when said separation chamber is substantially filled with fuel.7. The fuel system of claim 6 wherein said air separation chamber iscoupled to a vapor collection chamber which selectively stores saiddischarged amount of vapor.
 8. A variable volume fuel tank comprising: agenerally cylindrical housing including a first portion whichselectively receives and contains an amount of fuel, and a secondportion which selectively receives and contains an amount of pressurizedgas; a guide rod which is longitudinally mounted within said housing; apiston which is slidably disposed on said guide rod and which includesan inner lip and an outer lip; a first bellows member having a first endwhich is sealably connected to said outer lip of said piston and asecond end which is sealably connected to a back portion of saidhousing; and a second bellows member which is concentric to said firstbellows member and having a third end which is sealably connected tosaid inner lip of said piston and a fourth end which is sealablyconnected to said back portion of said housing; wherein said piston andsaid first and second bellows members cooperatively define said secondportion of said housing, and wherein said first and second bellowsmembers are selectively expandable, effective to cause said piston tomove within said housing and to compressibly pressurize said amount offuel.
 9. The variable volume fuel tank of claim 8 further comprising: asource of pressurized gas which is communicatively coupled to said backportion of said housing and which is effective to communicatepressurized gas into said second portion of said housing.
 10. Thevariable volume fuel tank of claim 9 wherein said amount of fuel withinsaid first portion has a certain average pressure and wherein saidsource of pressurized gas is effective to cause said amount of gaswithin said second portion to remain at approximately said certainaverage pressure during refueling.
 11. The variable volume fuel tank ofclaim 10 further comprising a separation chamber which is fluidlyconnected to said first portion, said separation chamber including anaperture which selectively allows an amount of vapor to be dischargedfrom said separation chamber and a float member which selectively sealssaid aperture when said separation chamber is substantially filled withfuel.
 12. A method for pressurizing an amount of fuel contained within afirst portion of a fuel tank, said method comprising the steps of:providing a piston; movably disposing said piston within said fuel tank;providing at least one selectively expandable diaphragm; sealablyconnecting a first end of said at least one selectively expandablediaphragm to a back surface of said fuel tank, said at least oneselectively expandable diaphragm being effective to define a secondportion of said fuel tank which is sealably separated from said firstportion of said fuel tank; and selectively introducing pressurized gasinto said second portion of said fuel tank, effective to cause said atleast one selectively expandable diaphragm to expand, thereby causingsaid piston to move within said variable volume fuel tank and tocompressibly pressurize said amount of fuel; wherein said at least oneselectively expandable diaphragm comprises a first bellows member havinga second end which is sealably connected to said piston and a secondbellows member concentric to said first bellows member and having athird end which is sealably connected to said piston.
 13. The method ofclaim 12 further comprising the steps of: providing a guide rod;mounting said piston on said guide rod; and longitudinally mounting saidguide rod within said fuel tank.
 14. The method of claim 12 wherein saidamount of fuel within said first portion has a certain average pressure,said method further comprising the steps of: causing said amount of gaswithin said second portion to remain at approximately said certainaverage pressure during refueling.